They still do this every April 1st in the U.K.? When I was living in the U.K. around 1978, I remember the topless convertible ad, where BMW used an air pump to blow air from the top of the windscreen so that a top wasn't needed in a rainstorm.
I'd love to see this tradition in the U.S., but I'm afraid we don't seem to have the humor for it over here... BMW would probably get a fine from the FTC for false advertising!
P.S. Here's a link to a clear picture of the ad:
BMW+Magnetic+Tow+Technology+April+Fool.jpg (image)
And the website link:
BMW UK : News
And the 2008 version:
http://www.bmweducation.co.uk/coFacts/images/C-R-A-P.jpg